The invention relates generally to thermal management techniques for use within an electrical apparatus and, more particularly, to interstitial structures for improving heat flow between an electrical component and a heat sink.
Many electrical components generate relatively large amounts of heat during periods of operation. This heat is most often the result of resistive losses within the components that are generally unavoidable. If this heat is not removed from the electrical component in an efficient manner, it will build up and dangerous temperatures may result. Electrical components operating at very high temperatures will often malfunction and can be permanently damaged. Therefore, thermal management techniques are often implemented within electrical circuits and systems to facilitate heat removal during periods of operation.
Thermal management techniques often involve the use of some form of heat sink to conduct heat away from high temperature areas in an electrical system. A heat sink is a structure formed from a high thermal conductivity material (e.g., typically a metal) that is mechanically coupled to an electrical component to aid in heat removal. In a relatively simple form, a heat sink can include a large piece of metal (e.g., aluminum or copper) that is clamped to an electrical circuit during operation. Heat from the electrical circuit flows into the heat sink through the mechanical interface between the units. Once in the heat sink, the heat is able to spread out and may also be radiated into the surrounding air space by the heat sink. If the mass and thermal conductivity of the heat sink is adequate, this may be all that is required to maintain an acceptable temperature level within the electrical component. In other cases, additional air or liquid cooling of the heat sink may be required. Many heat sinks include a series of fins or heat spreader plates for increasing the rate at which heat is transferred into the surrounding environment.
As described above, a heat sink is mechanically coupled to the heat producing component during operation. Typically, a flat surface of the heat sink will be held against a flat surface of the electrical component using some form of clamp or fastener. As can be appreciated, the surface of the heat sink and the surface of the component will rarely be perfectly planar or smooth, so air gaps will generally exist between the surfaces. As is generally well known, the existence of air gaps between two opposing surfaces reduces the ability to transfer heat through the interface between the surfaces. Thus, these air gaps reduce the effectiveness and value of the heat sink as a thermal management device. To address this problem, various thermal interface materials and structures (e.g., thermal greases and compliant pads) have been developed for placement between the heat transfer surfaces to decrease the thermal resistance there between. A thermal grease is a paste-like substance that is spread over one or both of the heat transfer surfaces before the surfaces are mated. When the surfaces are subsequently brought together, the thermal grease fills the air gaps between the surfaces, thus improving the thermal transfer properties of the interface. Thermal greases are typically difficult to apply and many tend to xe2x80x9cbleedxe2x80x9d from the thermal interface region or dry out during circuit operation. In addition, some thermal greases are conductive and can cause short circuits within an electrical system if care is not taken during application. A compliant pad is a thin flat structure that is placed between the heat transfer surfaces to reduce thermal resistance. Compliant pads are more convenient to use than thermal greases, but typically fall short in thermal transfer performance.
Therefore, there is a need for a thermal interface structure having enhanced thermal transfer characteristics.